1. Field of the Invention
The present invention relates to a mechanism for gradually and smoothly varying the rotational speed between a driving member and a driven member.
2. Description of the Related Art
It is sometimes necessary not to interconnect the driving shaft directly to the movement transmission members. This is all the more true when there is an internal combustion engine which cannot be started when engaged since it provides an appreciable torque only from a certain rotational speed.
The maximum driving torque available from a given engine is approximately constant, while the resistance to be overcome to ensure movement can vary continuously. In a motor-car, the propelling power must be equal to the repelling power so that it can move at a determined speed. The repelling torque varying continuously with the profile of the road, it would be desirable that the drive ratio between the rotational speeds of the engine and of the propeller shaft be responsive to the profile fluctuations, which amounts to having continuous gear shifting.
To vary the drive ratio, the following are generally used : gear boxes having various compound trains which can be activated at will, gearboxes having epicycloidal trains, torque converters as well as driving belt propeller means.
The use of these systems requires one to frequently modify the drive ratio according to the changes of the repelling power, which causes the engine speed to be varied and entails a specific consumption more significant than with a constant speed.
The mechanism according to the invention allows to overcome such drawbacks by enabling the speed changes in a continuous and progressive way, while enabling the engine to run at a constant speed.